package org.djutils.draw.point;
   
   import java.util.ArrayList;
   import java.util.Arrays;
   import java.util.Iterator;
   import java.util.List;
   import java.util.Locale;
   
   import org.djutils.draw.DrawRuntimeException;
  import org.djutils.draw.Drawable2d;
  import org.djutils.draw.bounds.Bounds2d;
  import org.djutils.draw.line.LineSegment2d;
  import org.djutils.exceptions.Throw;
  
  /**
   * A Point2d is an immutable Point with an x and y coordinate, stored with double precision. It differs from many Point
   * implementations by being immutable.
   * <p>
   * Copyright (c) 2020-2025 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="https://djutils.org/docs/current/djutils/licenses.html">DJUTILS License</a>.
   * </p>
   * @author <a href="https://www.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="https://github.com/peter-knoppers">Peter Knoppers</a>
   * @author <a href="https://github.com/wjschakel">Wouter Schakel</a>
   */
  public class Point2d implements Drawable2d, Point<Point2d>
  {
      /** */
      private static final long serialVersionUID = 20201201L;
  
      /** The x-coordinate. */
      @SuppressWarnings("checkstyle:visibilitymodifier")
      public final double x;
  
      /** The y-coordinate. */
      @SuppressWarnings("checkstyle:visibilitymodifier")
      public final double y;
  
      /**
       * Create a new Point2d from x and y coordinates provided as double arguments.
       * @param x the x coordinate
       * @param y the y coordinate
       * @throws IllegalArgumentException when <code>x</code>, or <code>y</code> is <code>NaN</code>
       */
      public Point2d(final double x, final double y)
      {
          Throw.whenNaN(x, "x");
          Throw.whenNaN(y, "y");
          this.x = x;
          this.y = y;
      }
  
      /**
       * Create a new Point2d from a x and y coordinates provided as values in a double array.
       * @param xy the x and y coordinates
       * @throws NullPointerException when <code>xy</code> is <code>null</code>
       * @throws IllegalArgumentException when the length of <code>xy</code> is not 2
       * @throws ArithmeticException when <code>xy</code> contains a <code>NaN</code> value
       */
      public Point2d(final double[] xy)
      {
          this(checkLengthIsTwo(Throw.whenNull(xy, "xy"))[0], xy[1]);
      }
  
      /**
       * Create an new Point2d from x and y obtained from a java.awt.geom.Point2D.
       * @param point a java.awt.geom.Point2D
       * @throws NullPointerException when <code>point</code> is <code>null</code>
       * @throws IllegalArgumentException when <code>point</code> has a <code>NaN</code> coordinate
       */
      public Point2d(final java.awt.geom.Point2D point) throws NullPointerException, IllegalArgumentException
      {
          Throw.whenNull(point, "point");
          Throw.whenNaN(point.getX(), "point.getX()");
          Throw.whenNaN(point.getY(), "point.getY()");
          this.x = point.getX();
          this.y = point.getY();
      }
  
      /**
       * Throw an IllegalArgumentException if the length of the provided array is not two.
       * @param xy the provided array
       * @return the provided array
       * @throws IllegalArgumentException when length of <code>xy</code> is not two
       */
      private static double[] checkLengthIsTwo(final double[] xy)
      {
          Throw.when(xy.length != 2, IllegalArgumentException.class, "Length of xy-array must be 2");
          return xy;
      }
  
      @Override
      public final double getX()
      {
          return this.x;
      }
  
      @Override
      public final double getY()
     {
         return this.y;
     }
 
     @Override
     public double distance(final Point2d otherPoint)
     {
         Throw.whenNull(otherPoint, "otherPoint");
         return Math.hypot(otherPoint.x - this.x, otherPoint.y - this.y);
     }
 
     @Override
     public double distanceSquared(final Point2d otherPoint) throws NullPointerException
     {
         Throw.whenNull(otherPoint, "otherPoint");
         double dx = this.x - otherPoint.x;
         double dy = this.y - otherPoint.y;
         return dx * dx + dy * dy;
     }
 
     @Override
     public int size()
     {
         return 1;
     }
 
     @Override
     public Iterator<Point2d> iterator()
     {
         return Arrays.stream(new Point2d[] {this}).iterator();
     }
 
     /**
      * Return a new Point2d with a translation by the provided dx and dy.
      * @param dX the x translation
      * @param dY the y translation
      * @return a new point with the translated coordinates
      * @throws IllegalArgumentException when <code>dX</code>, or <code>dY</code> is <code>NaN</code>
      */
     public Point2d translate(final double dX, final double dY)
     {
         Throw.whenNaN(dX, "dX");
         Throw.whenNaN(dY, "dY");
         return new Point2d(this.x + dX, this.y + dY);
     }
 
     /**
      * Return a new Point3d with a translation by the provided dx, dy and dz. If this is an OrientedPoint2d, then the result is
      * an OrientedPoint3d with rotX copied from this and rotY and rotZ are set to 0.0.
      * @param dX the x translation
      * @param dY the y translation
      * @param dZ the z translation
      * @return a new point with the translated coordinates
      * @throws IllegalArgumentException when <code>dX</code>, <code>dY</code>, or <code>dZ</code> is <code>NaN</code>
      */
     public Point3d translate(final double dX, final double dY, final double dZ)
     {
         Throw.whenNaN(dX, "dX");
         Throw.whenNaN(dY, "dY");
         Throw.whenNaN(dZ, "dZ");
         return new Point3d(this.x + dX, this.y + dY, dZ);
     }
 
     @Override
     public Point2d scale(final double factor)
     {
         Throw.whenNaN(factor, "factor");
         return new Point2d(this.x * factor, this.y * factor);
     }
 
     @Override
     public Point2d neg()
     {
         return scale(-1.0);
     }
 
     @Override
     public Point2d abs()
     {
         return new Point2d(Math.abs(this.x), Math.abs(this.y));
     }
 
     @Override
     public Point2d normalize() throws DrawRuntimeException
     {
         double length = Math.sqrt(this.x * this.x + this.y * this.y);
         Throw.when(length == 0.0, DrawRuntimeException.class, "cannot normalize (0.0, 0.0)");
         return this.scale(1.0 / length);
     }
 
     @Override
     public Point2d interpolate(final Point2d otherPoint, final double fraction)
     {
         Throw.whenNull(otherPoint, "otherPoint");
         Throw.whenNaN(fraction, "fraction");
         return new Point2d((1.0 - fraction) * this.x + fraction * otherPoint.x,
                 (1.0 - fraction) * this.y + fraction * otherPoint.y);
     }
 
     @Override
     public boolean epsilonEquals(final Point2d otherPoint, final double epsilon)
     {
         Throw.whenNull(otherPoint, "otherPoint");
         Throw.whenNaN(epsilon, "epsilon");
         Throw.when(epsilon < 0.0, IllegalArgumentException.class, "epsilon may not be negative");
         if (Math.abs(this.x - otherPoint.x) > epsilon)
         {
             return false;
         }
         if (Math.abs(this.y - otherPoint.y) > epsilon)
         {
             return false;
         }
         return true;
     }
 
     @Override
     public Bounds2d getBounds()
     {
         return new Bounds2d(this);
     }
 
     /**
      * Compute the 2D intersection of two lines. Both lines are defined by two points (that should be distinct).
      * @param line1P1X x-coordinate of start point of line 1
      * @param line1P1Y y-coordinate of start point of line 1
      * @param line1P2X x-coordinate of end point of line 1
      * @param line1P2Y y-coordinate of end point of line 1
      * @param lowLimitLine1 if<code>true</code>; the intersection may not lie before the start point of line 1
      * @param highLimitLine1 if<code>true</code>; the intersection may not lie beyond the end point of line 1
      * @param line2P1X x-coordinate of start point of line 2
      * @param line2P1Y y-coordinate of start point of line 2
      * @param line2P2X x-coordinate of end point of line 2
      * @param line2P2Y y-coordinate of end point of line 2
      * @param lowLimitLine2 if<code>true</code>; the intersection may not lie before the start point of line 2
      * @param highLimitLine2 if<code>true</code>; the intersection may not lie beyond the end point of line 2
      * @return the intersection of the two lines, or <code>null</code> if the lines are (almost) parallel, or the
      *         intersection point lies outside the permitted range
      * @throws ArithmeticException when any of the parameters is <code>NaN</code>
      */
     @SuppressWarnings("checkstyle:parameternumber")
     public static Point2d intersectionOfLines(final double line1P1X, final double line1P1Y, final double line1P2X,
             final double line1P2Y, final boolean lowLimitLine1, final boolean highLimitLine1, final double line2P1X,
             final double line2P1Y, final double line2P2X, final double line2P2Y, final boolean lowLimitLine2,
             final boolean highLimitLine2)
     {
         double line1DX = line1P2X - line1P1X;
         double line1DY = line1P2Y - line1P1Y;
         double l2p1x = line2P1X - line1P1X;
         double l2p1y = line2P1Y - line1P1Y;
         double l2p2x = line2P2X - line1P1X;
         double l2p2y = line2P2Y - line1P1Y;
         double denominator = (l2p2y - l2p1y) * line1DX - (l2p2x - l2p1x) * line1DY;
         Throw.whenNaN(denominator, "none of the parameters may be NaN");
         if (denominator == 0.0)
         {
             return null; // lines are parallel (they might even be on top of each other, but we don't check that)
         }
         double uA = ((l2p2x - l2p1x) * (-l2p1y) - (l2p2y - l2p1y) * (-l2p1x)) / denominator;
         // System.out.println("uA is " + uA);
         if (uA < 0.0 && lowLimitLine1 || uA > 1.0 && highLimitLine1)
         {
             return null; // intersection outside line 1
         }
         double uB = (line1DY * l2p1x - line1DX * l2p1y) / denominator;
         // System.out.println("uB is " + uB);
         if (uB < 0.0 && lowLimitLine2 || uB > 1.0 && highLimitLine2)
         {
             return null; // intersection outside line 2
         }
         if (uA == 1.0) // maximize precision
         {
             return new Point2d(line1P2X, line1P2Y);
         }
         if (uB == 0.0)
         {
             return new Point2d(line2P1X, line2P1Y);
         }
         if (uB == 1.0)
         {
             return new Point2d(line2P2X, line2P2Y);
         }
         return new Point2d(line1P1X + uA * line1DX, line1P1Y + uA * line1DY);
     }
 
     /**
      * Compute the 2D intersection of two lines. Both lines are defined by two points (that should be distinct). The lines are
      * considered to be infinitely long; so unless the lines are parallel; there is an intersection.
      * @param l1P1X x-coordinate of start point of line segment 1
      * @param l1P1Y y-coordinate of start point of line segment 1
      * @param l1P2X x-coordinate of end point of line segment 1
      * @param l1P2Y y-coordinate of end point of line segment 1
      * @param l2P1X x-coordinate of start point of line segment 2
      * @param l2P1Y y-coordinate of start point of line segment 2
      * @param l2P2X x-coordinate of end point of line segment 2
      * @param l2P2Y y-coordinate of end point of line segment 2
      * @return the intersection of the two lines, or <code>null</code> if the lines are (almost) parallel
      * @throws ArithmeticException when any of the parameters is <code>NaN</code>
      */
     @SuppressWarnings("checkstyle:parameternumber")
     public static Point2d intersectionOfLines(final double l1P1X, final double l1P1Y, final double l1P2X, final double l1P2Y,
             final double l2P1X, final double l2P1Y, final double l2P2X, final double l2P2Y)
     {
         return intersectionOfLines(l1P1X, l1P1Y, l1P2X, l1P2Y, false, false, l2P1X, l2P1Y, l2P2X, l2P2Y, false, false);
     }
 
     /**
      * Compute the 2D intersection of two lines. Both lines are defined by two points (that should be distinct). The lines are
      * considered to be infinitely long; so unless the lines are parallel; there is an intersection.
      * @param line1P1 first point of line 1
      * @param line1P2 second point of line 1
      * @param line2P1 first point of line 2
      * @param line2P2 second point of line 2
      * @return the intersection of the two lines, or <code>null</code> if the lines are (almost) parallel
      * @throws NullPointerException when any of the points is <code>null</code>
      */
     public static Point2d intersectionOfLines(final Point2d line1P1, final Point2d line1P2, final Point2d line2P1,
             final Point2d line2P2)
     {
         Throw.whenNull(line1P1, "line1P1");
         Throw.whenNull(line1P2, "line1P2");
         Throw.whenNull(line2P1, "line2P1");
         Throw.whenNull(line2P2, "line2P2");
         return intersectionOfLines(line1P1.x, line1P1.y, line1P2.x, line1P2.y, false, false, line2P1.x, line2P1.y, line2P2.x,
                 line2P2.y, false, false);
     }
 
     /**
      * Compute the 2D intersection of two line segments. Both line segments are defined by two points (that should be distinct).
      * @param line1P1 first point of line segment 1
      * @param line1P2 second point of line segment 1
      * @param line2P1 first point of line segment 2
      * @param line2P2 second point of line segment 2
      * @return the intersection of the two line segments, or <code>null</code> if the lines are parallel (within
      *         rounding error), or do not intersect
      * @throws NullPointerException when any of the points is <code>null</code>
      * @throws DrawRuntimeException when any of the line segments is ill-defined (begin point equals end point), or the two line
      *             segments are parallel or overlapping
      */
     public static Point2d intersectionOfLineSegments(final Point2d line1P1, final Point2d line1P2, final Point2d line2P1,
             final Point2d line2P2)
     {
         Throw.whenNull(line1P1, "line1P1");
         Throw.whenNull(line1P2, "line1P2");
         Throw.whenNull(line2P1, "line2P1");
         Throw.whenNull(line2P2, "line2P2");
         return intersectionOfLines(line1P1.x, line1P1.y, line1P2.x, line1P2.y, true, true, line2P1.x, line2P1.y, line2P2.x,
                 line2P2.y, true, true);
     }
 
     /**
      * Compute the 2D intersection of two line segments. Both line segments are defined by two points (that should be distinct).
      * @param line1P1X x coordinate of start point of first line segment
      * @param line1P1Y y coordinate of start point of first line segment
      * @param line1P2X x coordinate of end point of first line segment
      * @param line1P2Y y coordinate of end point of first line segment
      * @param line2P1X x coordinate of start point of second line segment
      * @param line2P1Y y coordinate of start point of second line segment
      * @param line2P2X x coordinate of end point of second line segment
      * @param line2P2Y y coordinate of end point of second line segment
      * @return the intersection of the two line segments, or <code>null</code> if the lines are parallel (within
      *         rounding error), or do not intersect
      * @throws ArithmeticException when any of the values is <code>NaN</code>
      */
     @SuppressWarnings("checkstyle:parameternumber")
     public static Point2d intersectionOfLineSegments(final double line1P1X, final double line1P1Y, final double line1P2X,
             final double line1P2Y, final double line2P1X, final double line2P1Y, final double line2P2X, final double line2P2Y)
     {
         return intersectionOfLines(line1P1X, line1P1Y, line1P2X, line1P2Y, true, true, line2P1X, line2P1Y, line2P2X, line2P2Y,
                 true, true);
     }
 
     /**
      * Compute the 2D intersection of two line segments.
      * @param segment1 the first line segment
      * @param segment2 the other line segment
      * @return the intersection of the line segments, or <code>null</code> if the line segments do not intersect
      */
     public static Point2d intersectionOfLineSegments(final LineSegment2d segment1, final LineSegment2d segment2)
     {
         return intersectionOfLineSegments(segment1.startX, segment1.startY, segment1.endX, segment1.endY, segment2.startX,
                 segment2.startY, segment2.endX, segment2.endY);
     }
 
     @Override
     public Point2d closestPointOnSegment(final Point2d segmentPoint1, final Point2d segmentPoint2)
     {
         Throw.whenNull(segmentPoint1, "segmentPoint1");
         Throw.whenNull(segmentPoint2, "segmentPoint2");
         return closestPointOnSegment(segmentPoint1.x, segmentPoint1.y, segmentPoint2.x, segmentPoint2.y);
     }
 
     /**
      * Compute the closest point on a line with optional limiting of the result on either end.
      * @param p1X the x coordinate of the first point on the line
      * @param p1Y the y coordinate of the first point on the line
      * @param p2X the x coordinate of the second point on the line
      * @param p2Y the y coordinate of the second point on the line
      * @param lowLimitHandling controls handling of results that lie before the first point of the line. If
      *            <code>null</code>; this method returns <code>null</code>; else if <code>true</code>; this method returns
      *            (p1X,p1Y); else (lowLimitHandling is <code>false</code>); this method will return the closest point on the
      *            line
      * @param highLimitHandling controls the handling of results that lie beyond the second point of the line. If
      *            <code>null</code>; this method returns <code>null</code>; else if <code>true</code>; this method returns
      *            (p2X,p2Y); else (highLimitHandling is <code>false</code>); this method will return the closest point on the
      *            line
      * @return the closest point on the line after applying the indicated limit handling; so the result can be
      *         <code>null</code>
      * @throws ArithmeticException when any of the arguments is <code>NaN</code>
      * @throws DrawRuntimeException when the line is ill-defined (begin point coincides with end point)
      */
     public Point2d closestPointOnLine(final double p1X, final double p1Y, final double p2X, final double p2Y,
             final Boolean lowLimitHandling, final Boolean highLimitHandling)
     {
         double fraction = fractionalPositionOnLine(p1X, p1Y, p2X, p2Y, lowLimitHandling, highLimitHandling);
         if (Double.isNaN(fraction))
         {
             return null;
         }
         if (fraction == 1.0)
         {
             return new Point2d(p2X, p2Y); // Maximize precision in case fraction == 1.0
         }
         return new Point2d(p1X + fraction * (p2X - p1X), p1Y + fraction * (p2Y - p1Y));
     }
 
     /**
      * Compute the fractional position of the closest point on a line with optional limiting of the result on either end. If the
      * line has length 0; this method returns 0.0.
      * @param p1X the x coordinate of the first point on the line
      * @param p1Y the y coordinate of the first point on the line
      * @param p2X the x coordinate of the second point on the line
      * @param p2Y the y coordinate of the second point on the line
      * @param lowLimitHandling controls handling of results that lie before the first point of the line. If
      *            <code>null</code>; this method returns <code>NaN</code>; else if <code>true</code>; this method returns 0.0;
      *            else (lowLimitHandling is <code>false</code>); this results &lt; 0.0 are returned
      * @param highLimitHandling controls the handling of results that lie beyond the second point of the line. If
      *            <code>null</code>; this method returns <code>NaN</code>; else if <code>true</code>; this method returns 1.0;
      *            else (highLimitHandling is <code>false</code>); results &gt; 1.0 are returned
      * @return the fractional position of the closest point on the line. Results within the range 0.0 .. 1.0 are always
      *         returned as is.. A result &lt; 0.0 is subject to lowLimitHandling. A result &gt; 1.0 is subject to
      *         highLimitHandling
      * @throws ArithmeticException when any of the arguments is NaN
      * @throws DrawRuntimeException when the line is ill-defined (begin point coincides with end point)
      */
     public double fractionalPositionOnLine(final double p1X, final double p1Y, final double p2X, final double p2Y,
             final Boolean lowLimitHandling, final Boolean highLimitHandling)
     {
         double dX = p2X - p1X;
         double dY = p2Y - p1Y;
         Throw.whenNaN(dX, "dX");
         Throw.whenNaN(dY, "dY");
         if (0 == dX && 0 == dY)
         {
             return 0.0;
         }
         double fraction = ((this.x - p1X) * dX + (this.y - p1Y) * dY) / (dX * dX + dY * dY);
         if (fraction < 0.0)
         {
             if (lowLimitHandling == null)
             {
                 return Double.NaN;
             }
             if (lowLimitHandling)
             {
                 fraction = 0.0;
             }
         }
         else if (fraction > 1.0)
         {
             if (highLimitHandling == null)
             {
                 return Double.NaN;
             }
             if (highLimitHandling)
             {
                 fraction = 1.0;
             }
         }
         return fraction;
     }
 
     /**
      * Project a point on a line segment. If the the projected points lies outside the line segment, the nearest end point of
      * the line segment is returned. Otherwise the returned point lies between the end points of the line segment. <br>
      * Adapted from <a href="http://paulbourke.net/geometry/pointlineplane/DistancePoint.java">example code provided by Paul
      * Bourke</a>.
      * @param p1X the x coordinate of the start point of the line segment
      * @param p1Y the y coordinate of the start point of the line segment
      * @param p2X the x coordinate of the end point of the line segment
      * @param p2Y the y coordinate of the end point of the line segment
      * @return either <code>segmentPoint1</code>, or <code>segmentPoint2</code> or a new Point2d that lies somewhere in
      *         between those two.
      * @throws DrawRuntimeException when the line is ill-defined (begin point coincides with end point)
      */
     public final Point2d closestPointOnSegment(final double p1X, final double p1Y, final double p2X, final double p2Y)
     {
         return closestPointOnLine(p1X, p1Y, p2X, p2Y, true, true);
     }
 
     @Override
     public Point2d closestPointOnLine(final Point2d linePoint1, final Point2d linePoint2)
             throws NullPointerException, DrawRuntimeException
     {
         Throw.whenNull(linePoint1, "linePoint1");
         Throw.whenNull(linePoint2, "linePoint2");
         return closestPointOnLine(linePoint1.x, linePoint1.y, linePoint2.x, linePoint2.y);
     }
 
     /**
      * Project a point on a line. <br>
      * Adapted from <a href="http://paulbourke.net/geometry/pointlineplane/DistancePoint.java">example code provided by Paul
      * Bourke</a>.
      * @param p1X the x coordinate of a point of the line segment
      * @param p1Y the y coordinate of a point of the line segment
      * @param p2X the x coordinate of another point of the line segment
      * @param p2Y the y coordinate of another point of the line segment
      * @return a point on the line that goes through the points
      * @throws IllegalArgumentException when the points on the line are identical
      */
     public final Point2d closestPointOnLine(final double p1X, final double p1Y, final double p2X, final double p2Y)
     {
         Throw.when(p1X == p2X && p1Y == p2Y, IllegalArgumentException.class, "degenerate line not allowed");
         return closestPointOnLine(p1X, p1Y, p2X, p2Y, false, false);
     }
 
     /**
      * Return the zero, one or two intersections between two circles. The circles must be different. Derived from pseudo code by
      * <a href="http://paulbourke.net/geometry/circlesphere/">Paul Bourke</a> and C implementation by
      * <a href="http://paulbourke.net/geometry/circlesphere/tvoght.c">Tim Voght </a>.
      * @param center1 the center of circle 1
      * @param radius1 the radius of circle 1
      * @param center2 the center of circle 2
      * @param radius2 the radius of circle 2
      * @return List&lt;Point2d&gt; a list of zero, one or two points
      * @throws NullPointerException when <code>center1</code> or <code>center2</code> is <code>null</code>
      * @throws IllegalArgumentException when the two circles are identical, or <code>radius1 &lt; 0.0</code>, or
      *             <code>radius2 &lt; 0.0</code>
      */
     public static final List<Point2d> circleIntersections(final Point2d center1, final double radius1, final Point2d center2,
             final double radius2) throws NullPointerException, IllegalArgumentException
     {
         Throw.whenNull(center1, "center1");
         Throw.whenNull(center2, "center2");
         Throw.when(radius1 < 0 || radius2 < 0, IllegalArgumentException.class, "radius may not be less than 0");
         Throw.when(center1.equals(center2) && radius1 == radius2, IllegalArgumentException.class, "circles must be different");
         List<Point2d> result = new ArrayList<>();
         // dX,dY is the vector from center1 to center2
         double dX = center2.x - center1.x;
         double dY = center2.y - center1.y;
         double distance = Math.hypot(dX, dY);
         if (distance > radius1 + radius2 || distance < Math.abs(radius1 - radius2))
         {
             return result; // empty list
         }
         double a = (radius1 * radius1 - radius2 * radius2 + distance * distance) / (2 * distance);
         // x2,y2 is the point where the line through the circle intersections crosses the line through the circle centers
         double x2 = center1.x + (dX * a / distance);
         double y2 = center1.y + (dY * a / distance);
         // h is distance from x2,y2 to each of the solutions
         double h = Math.sqrt(radius1 * radius1 - a * a);
         // rX, rY is vector from x2,y2 to the first solution
         double rX = -dY * (h / distance);
         double rY = dX * (h / distance);
         result.add(new Point2d(x2 + rX, y2 + rY));
         if (h > 0)
         {
             // Two distinct solutions; add the second one
             result.add(new Point2d(x2 - rX, y2 - rY));
         }
         return result;
     }
 
     /**
      * Return the direction to another Point2d.
      * @param otherPoint the other point
      * @return the direction to the other point in Radians (towards infinite X is 0; towards infinite Y is &pi; / 2;
      *         etc.). If the points are identical; this method returns <code>NaN</code>.
      */
     public double directionTo(final Point2d otherPoint)
     {
         return Math.atan2(otherPoint.y - this.y, otherPoint.x - this.x);
     }
 
     /**
      * Return the coordinates as a java.awt.geom.Point2D.Double object.
      * @return java.awt.geom.Point2D; the coordinates as a java.awt.geom.Point2D.Double object
      */
     public java.awt.geom.Point2D toPoint2D()
     {
         return new java.awt.geom.Point2D.Double(this.x, this.y);
     }
 
     @Override
     public String toString()
     {
         return toString("%f");
     }
 
     @Override
     public String toString(final String doubleFormat, final boolean doNotIncludeClassName)
     {
         String format = String.format("%1$s[x=%2$s, y=%2$s]", doNotIncludeClassName ? "" : "Point2d ", doubleFormat);
         return String.format(Locale.US, format, this.x, this.y);
     }
 
     @Override
     public int hashCode()
     {
         final int prime = 31;
         int result = 1;
         long temp;
         temp = Double.doubleToLongBits(this.x);
         result = prime * result + (int) (temp ^ (temp >>> 32));
         temp = Double.doubleToLongBits(this.y);
         result = prime * result + (int) (temp ^ (temp >>> 32));
         return result;
     }
 
     @SuppressWarnings("checkstyle:needbraces")
     @Override
     public boolean equals(final Object obj)
     {
         if (this == obj)
             return true;
         if (obj == null)
             return false;
         if (getClass() != obj.getClass())
             return false;
         Point2d other = (Point2d) obj;
         if (Double.doubleToLongBits(this.x) != Double.doubleToLongBits(other.x))
             return false;
         if (Double.doubleToLongBits(this.y) != Double.doubleToLongBits(other.y))
             return false;
         return true;
     }
 
 }